The red-footed booby is the smallest of all boobies at about 70 centimetres (28 in) in length and with a wingspan of up to 1 metre (3.3 ft). It has red legs, and its bill and throat pouch are coloured pink and blue.

This species has several morphs. In the white morph the plumage is mostly white (the head often tinged yellowish) and the flight feathers are black. The black-tailed white morph is similar, but with a black tail, and can easily be confused with the Nazca and masked boobies.

The brown morph is overall brown. The white-tailed brown morph is similar, but has a white belly, rump, and tail. The white-headed and white-tailed brown morph has a mostly white body, tail and head, and brown wings and back.